Numerous attempts have been made in the prior art to develop an optical coupler which effectively, efficiently, and inexpensively couples light bewteen an optical fiber and a light emitter such as a light emitting diode (LED), laser, or photodetector. Though numerous approaches have been specified, many require that the optical fiber be terminated and spliced to a coupling device which is disadvantageous since splicing tends to be a craft sensitive and expensive procedure, and splicing also results in unacceptably high optical losses.
Some approaches have avoided the cost and other problems associated with splicing a discreet optical coupler device into an optical fiber network by proposing to pass the light through a side of the optical fiber, preferably at a bend in the fiber, so as to pass light through a cladding of the fiber which surrounds a core of the fiber, and optimally one or more buffer layers surrounding the cladding. One such method which has obtained positive results is disclosed by Uken in U.S. Pat. No. 4,741,585, one of the coinventors herein, the disclosure of which is incorporated herein by reference. Uken teaches coupling light from between a core of an optical fiber which is bent so as to be disposed in a plane, deflecting the light out of the plane so as to pass through a substrate in a direction substantially perpendicular to the fiber plane, and locating a light element along this substantially perpendicular direction. Though this approach results in an optical coupler design which is inexpensive to produce and which produces favorable optical coupling efficiencies, a need continues to exist to improve these efficiencies in applications where optical flux budgets are tight, and a need continues to further simplify the coupler design in networking applications where electrical transmission systems such as copper already offer low cost data transmission solutions.